Metabolism of norethisterone in the greyhound

Abstract

The urinary metabolites identified in this study have further increased the knowledge of steroid metabolism in the greyhound, providing information to support routine drug testing programmes for greyhound racing.

Investigations into the analysis of intact drug conjugates in animal sport doping control – Development and assessment of a rapid and economical approach for screening greyhound urine

“…As per the work described by Biddle et al several norethisterone metabolites are detected in canine urine following administration, with the major metabolites being various diols, triols, and tetrols. These metabolites are excreted primarily as intact glucuronide conjugates and hence should be suitable for inclusion within the POR method.…”

“…The selection of appropriate analytes for inclusion in the method was based upon a number of factors, primarily the experience available within the laboratory, gained from many years of analyzing race‐day canine urine samples [unpublished], along with reference to published work on the metabolism of anabolic steroids in the canine . As per the work presented by Mckinney et al three compounds were included for the detection of boldenone.…”

“…Boldenone glucuronide itself, an A‐ring reduced metabolite (boldenone metabolite 1 glucuronide), and an A‐ring reduced metabolite with further reduction of the 3‐ketone (boldenone metabolite 2 glucuronide). For the detection of nandrolone, two glucuronide conjugated metabolites were selected for inclusion in the method, being 19‐norepiandrosterone glucuronide and 19‐noreticholanolone glucuronide . Detection of stanozolol was achieved via the monitoring of three analytes, glucuronidated stanozolol itself and mono‐ and di‐hydroxylated stanozolol conjugates …”

“…Once established and in routine use the analysis of genuine POR samples demonstrated that there were a number of adverse screening findings for nandrolone metabolites that were occurring in bitch urine. Previous work by Biddle et al had shown that nandrolone metabolites could be present in bitch urine as a result of the administration of norethisterone, which is given in order to control the estrus cycle. These metabolites arise as a result of the presence of low level contamination of the norethisterone tablets with nandrolone and 19‐norandrostenedione.…”

“…In 2011, the GBGB permitted the use of norethisterone as an estrus suppressant in racing greyhounds . Investigation of its administration to greyhounds has previously been shown to lead to the detection of the nandrolone metabolites 19‐noreticholanalone and 19‐norepiandrosterone in female greyhounds, due to the presence of nandrolone and 19‐norandrostenedione as low level contaminants within the norethisterone tablets …”